1. Field of the Invention
The present invention relates to flexible harnesses composed of a flexible printed circuit board (which is an insulator film on that a conductor pattern is formed). The invention particularly relates to detachable flexible harnesses and electrical connector cables using such a flexible harness used for connection between various electric/electronic components such as printed circuit boards and IC (integrated circuit) chips.
2. Description of Related Art
Flexible harnesses are often used for electrical connection between various electric/electronic components such as printed circuit boards and IC chips. Flexible harnesses are composed of a flexible printed circuit board (which is a flexible insulator film on that a conductor pattern is formed). End terminals of the conductor pattern are electrically connected to electrode pads of an electric/electronic component. Thus, electrical connection between various electric/electronic components is provided. The flexible harnesses are detachable and, therefore, have advantages that exchange of electric/electronic components (such as components mounted on a device) and electric/electronic devices (such as peripherals) is simplified, and also assembly of the electric/electronic apparatuses is facilitated.
In connecting a flexible harness to an electric/electronic component, it is important to provide stable physical contact and electrical connection between terminal ends of the conductor lines of the conductor pattern of the flexible harness and the electrode pads of the electric/electronic component. So, usually, the electric/electronic component (to which a flexible harness is to be connected) is provided with a receptacle (or a female connector) for fitting together the end terminals of the conductor lines of the flexible harness.
An example of such a receptacle is reported in, e.g., JP-A Hei 6(1994)-68940, in which multiple spring conductors (which are metal electrodes formed by molding or the like) are fitted in a plastic cover, and are electrically connected to a component such as a printed circuit board and an IC chip. When a flexible harness is fitted into such a receptacle, the spring conductors fit together with the end terminals of the conductor lines of the flexible harness.
Another example of such a receptacle type connector is reported in, e.g., JP-A Hei 11(1697)-31543, in which an insulator member having a protrusion covered with a conductor is formed in the receptacle, and a member having a recession (which is covered with a conductor and can receive the protrusion formed in the receptacle) is formed in the connector of the flexible harness. With this structure, electrical contact is provided by fitting the protrusion into the recession.
In some flexible harnesses, the end terminals of the conductor lines of the flexible harness are backed by a reinforcing rigid plate in order to resist the force exerted by the electrodes of a receptacle to the end terminals.
Electronic components such as IC chips are continually being downsized. Also, the number of pins on such electronic components continues to rise, and as a result the pin pitch continues to decrease. As described above, conventional receptacles are configured by, for example, fitting multiple resilient conductor electrodes in a plastic cover. However, it is difficult to downsize such conventional receptacles or increase the number of electrode pins in such conventional receptacles. In particular, for devices having a pin array of multiple rows and columns (such as a pin grid array and a land grid array), it is even more difficult to form a receptacle having an array of multiple resilient conductors. Even if the formation of such a receptacle having a resilient electrode array is possible, its manufacturing cost will be unacceptably high.
A possible solution to the above problems is to force end terminals of the conductor lines of the flexible harness to directly contact the electrode pads of an electric/electronic component without using a receptacle. However, the end terminals of the conductor lines of the flexible harness do not have spring properties and, therefore, it is difficult to evenly apply sufficient contact force to all the contact points. For example, when there is even a slight difference among the heights of the electrode pads of the electric/electronic component, then stable and reliable electrical connection may not be established at some of the contact points. For another example, when a printed circuit board (to which a flexible harness is to be connected) warps, electrical connection may not be established at many of the contact points between the flexible harness and the printed circuit board because the end terminals of the flexible harness do not have spring properties.